Cell polarization relies on small GTPases, such as Cdc42, which can break symmetry through self-organizing principles, and landmarks that define the axis of polarity. In fission yeast, microtubules deliver the Tea1-Tea4 complex to mark cell poles for growth, but how this complex activates Cdc42 is unknown. Here we show that ectopic targeting of Tea4 to cell sides promotes Cdc42 local activation and cell growth. This activity requires Tea4 binding type I phosphatase (PP1) catalytic subunit Dis2 or Sds21, and ectopic targeting of either catalytic subunit is similarly instructive for growth. Cdc42 Guanine nucleotide Exchange Factor Gef1 and GTPase-activating protein Rga4 are required for Tea4-PP1-dependent ectopic growth. Gef1 is recruited to ectopic Tea4 and Dis2 locations for Cdc42 activation. By contrast, Rga4 is locally excluded by Tea4 and forced colocalization with Tea4 blocks ectopic growth, indicating Rga4 must be present but at sites distinct from Tea4. Thus, a Tea4-PP1 landmark promotes local Cdc42 activation and growth both through Cdc42 GEF recruitment and by creating a local trough in a Cdc42 GAP.